Autochthonous versus allochthonous carbon sources of bacteria: results from whole-lake Carbon-13 addition experiments
Bibliographic record
Abstract
Organic substrates for pelagic bacteria are derived from dissolved organic carbon (DOC) in the water column.DOC is a heterogeneous mixture of molecules, some of which are imported from the watershed (allochthonous DOC) and others that are produced by autotrophs within the system (autochthonous DOC).We examined the importance of autochthonous versus allochthonous DOC in supporting the growth of pelagic bacteria by manipulating the 13 C content of autochthonous sources in a whole-lake experiment.NaH 13 CO 3 was added daily to two small forested lakes for a period of 42 d, thereby strongly labeling autochthonous primary production.To obtain bacterial carbon isotopes, bacteria were regrown in vitro in particle-free lake water and in situ in dialysis tubes; little difference was found between the two methods.The contribution of autochthonous versus allochthonous carbon to the bacterial biomass was estimated by applying a two-member mixing model using a 13 C of 28 as the allochthonous end member.The autochthonous end member, which varied over time, was estimated indirectly by several approaches.The bacterial biomass consisted of 35-70% allochthonous carbon.This result confirms the often-stated hypothesis that autochthonous carbon alone does not support bacterial production.On the other hand, autochthonous DOC was preferentially utilized relative to terrestrial DOC.On the basis of 13 C measurements, only 13% of the DOC standing stock was of recent autochthonous origin, but it supported 30-65% of bacterial production.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".